|LI, WENTING - Dupont Industrial Biosciences|
|ANGEL, ROSELINA - University Of Maryland|
|KIM, SEON-WOO - University Of Maryland|
|JIMENEZ-MORENO, ENCARNACION - Cargill Slu, Cargill Animal Nutrition|
|PLUMSTEAD, PETER - University Of Pretoria|
Submitted to: Animal Feed Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2018
Publication Date: 2/6/2018
Citation: Li, W., Angel, R., Kim, S., Jimenez-Moreno, E., Proszkowiec-Wegla, M.K., Plumstead, P.W. 2018. Impacts of age and calcium on Phytase efficacy in broiler chickens. Animal Feed Science And Technology. 238:9-17.
Interpretive Summary: Phosphorus (P) is the third most expensive feed ingredient in poultry industry following protein and energy. Typical corn-soybean meal based poultry diet contains between 40-60% of P in the form of phytate-P. The availability of P from phytate-P varies and can be affected by many factors including presence of calcium (Ca) and phytase (enzyme releasing P from phytate-P). Impacts of Ca and phytase on P digestibility (utilisation level by the birds) have been examined extensively in the past two decades. However, most of the studies were conducted in broilers around 21 days of age, and did not test for an age effect. Young birds are characterized by not fully developed digestive tract and faster passage rate. Without fully understanding the impact of age on phytase efficacy and Ca impact, it is difficult to optimize phytase efficacy and phytate-P utilization as well as minimize use and dependency on inorganic P. Therefore, the aim of the present study was to (1) determine the impact of Ca on the efficacy of a new generation Buttiauxella 6-phytase in 9 and 21 days old broiler birds and to (2) determine the impact of age on the responses to diet Ca and phytase on apparent ileal P digestibility. A total of 648 broiler birds were fed corn and soybean-meal based diets with 0.19% non-phytate-P with three Ca (6.5, 8.0 and 9.5 g/kg) concentrations. At each Ca concentration, a 6-phytase was added on-top at 0, 500 or 1000 phytase unit (FTU)/kg. Broiler birds were fed the diets for 2 days either from 7 to 9 or 19 to 21 days of age, and ileal content was collected from all birds at the end of each feeding period to determine apparent ileal digestibility coefficient. Age effect was determined by comparing responses between birds fed from 7 to 9 and 19 to 21 days of age. The results indicate that (1) higher P digestibility were observed in older birds in comparison to younger birds, (2) the response to Ca and phytase was affected by broiler age, (3) birds at different ages responded to Ca and phytase similarly, however in younger broilers the detrimental effect of Ca was more severe and the effects of phytase inclusion were greater, and (4 )increase in P digestibility was observed with increasing dose of phytase. The results also suggest that using a high dose of phytase to help degrade phytate as much as possible in the upper digestive tract could significantly alleviate the Ca impact and maximize P digestibility.
Technical Abstract: A total of 648 straight-run hatchling Heritage 56M × fast feathering Cobb 500F broiler birds were used to determine the effects of Ca concentration and age on phytase efficacy. Corn and SBM based diets with 0.19%non-phytate P were prepared with three Ca (6.5, 8.0 and 9.5 g/kg) concentrations. A 6-phytase was added on-top at 0, 500 or 1000 FTU/kg at each Ca concentration, resulting in a total of 9 treatments. Broiler birds were fed the diets for 2 d either from 7 to 9 (6 birds/replicate) or 19 to 21 (3 birds/replicate) d of age, and ileal content was collected from every bird at the end of each feeding period to determine apparent ileal digestibility coefficient (AID). Age effect was determined by comparing responses between birds fed from 7 to 9 and 19 to 21 d of age. There was no interaction between Ca and phytase on AID P regardless of age. Increasing Ca from 6.5 to 9.5 g/kg resulted in 12 (0.58 vs. 0.51) and 11% (0.64 vs. 0.57) reduction in AID P, in 9-d-old and 21-d-old birds, respectively (P<0.05). Compared to birds fed diets without phytase, AID P was 100 and 155% greater in 9 d old birds fed 500 and 1000 FTU phytase/kg diets, respectively (P<0.05). Similar but lesser improvement in AID P was also seen in 21 d old birds, with 63 and 76% improvement as a result of 500 and 1000 FTU/kg phytase inclusion, respectively (P<0.05). Despite similar pattern in response to Ca and phytase, the degree of dietary impact and efficacy of phytase was affected by age of birds. In the absence of phytase, detrimental effect of Ca was more apparent in 9 d old than 21 d old bird, where greater difference in AID P was seen when Ca increased from 6.5 to 9.5 g/kg. With phytase inclusion, differences in AID P between 9 and 21 d old birds were reduced, which was more apparent with higher phytase and Ca inclusion. Net improvement of digestible P for 500 and 1000 FTU phytase/kg was 1.55 and 2.42, 1.45 and 1.72 g/kg, respectively for 9 and 21 d old birds. It is clearly shown that, even though birds at different ages responded to Ca and phytase similarly, the detrimental impact of Ca and benefit of phytase inclusion was greater in younger than older birds.